Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
H, W = map(int, input().split())
S = [input() for _ in range(H)]
white = sum(s.count(".") for s in S)
visited = [[-1] * W for _ in range(H)]
deq = deque([(0,0)])
visited[0][0] = 1
dia = [1, 0, -1, 0, 1]
while deq:
    i, j = deq.popleft()
    if i == H - 1 and j == W - 1:
        break
    d = visited[i][j]
    for x, y in zip(dia, dia[1:]):
        ii, jj = i + x, j + y
        if 0 <= ii < H and 0 <= jj < W and S[ii][jj] == "." and visited[ii][jj] < 0:
            visited[ii][jj] = d + 1
            deq.append((ii, jj))
print(white - visited[H-1][W-1] if visited[H-1][W-1] > 0 else -1)